This invention relates to an improved egg carton, and to methods of making it.
U.S. Pat. No. 2,990,094 shows an egg carton with a latch of the type in which a "button" on the latch flap extends through a hole in the flat surface of the cover to latch the carton closed. Problems were experienced with this type of egg carton because persons picking the carton up by the cover inadvertently pushed the protrusion out of engagement with the hole, thereby unlatching the egg carton with disastrous results.
Cartons of the type shown in U.S. Pat. No. 3,648,916-Commisso obviate this problem. The latch flap has a locking recess which includes a latch bar across the top thereof. The cover has recesses which are complementary to the recess on the latch flap. A hole is cut across the recess in the cover. This hole extends from the flat surface of the front of the cover down into the recess, across the recess, and back to the front surface of the cover. In the closed position, the latching bar fits into this hole to hold the cover in the closed position. This latching mechanism has the advantage that it is recessed. Therefore, when the carton is grasped by the cover, there is no possibility of inadvertently unlatching the cover.
Egg cartons of the type shown in the Commisso patent have been successfully used for packaging a dozen eggs. The cartons are easily produced in large quantities by thermoforming a sheet of preheated polystyrene foam.
An egg carton fabrication technique which preceded that of thermoforming is the molding of cartons from pulp. In such a process, semi-liquid pulp is sprayed or otherwise inserted into a mold having the desired configuration. U.S. Pat. No. 3,215,327-Crabtree shows an example of a molded pulp carton. Pulp cartons have been extensively and successfully used. However, the recent trend has been toward thermoformed plastic cartons because of improved appearance and economies of production over molded pulp cartons.
In some markets, eggs are sold in cartons of eighteen eggs, rather than in the traditional "dozen" carton. Heretofore, eighteen cell egg cartons have been thermoformed from plastic sheet only in a version which does not have a protective cover. An eighteen cell carton with protective cover has been produced in molded pulp. It is desirable to thermoform an eighteen cell egg carton with a protective cover which can be latched to the cell section when the carton is closed. However, the existing covered eighteen cell cartons such as the pulp carton presently on the market, cannot be thermoformed from plastic sheet. For one reason, the latch of such a carton has long elements, which, if thermoformed, would entail a severe extension beyond the sheet line. In thermoforming, extensions beyond the sheet line are undesirable because severe extensions produce weakened plastic elements.
Furthermore, existing thermoformed cartons, such as that shown in the Commisso patent, cannot be simply expanded to accommodate eighteen eggs. One of the requirements for egg cartons is that they be suitable for use in existing packaging equipment. A large amount of packaging equipment has already been placed in the field for packaging eggs. This packaging equipment accepts both covered twelve cell and coverless eighteen cell egg cartons. Alternatively, this same equipment has been used to process the covered pulp cartons which have a cell section which is 6" by 12" and a cover which is 6" by 12". The reason that thermoformed cartons, such as that shown in the Commisso patent, cannot be expanded to an eighteen cell configuration is that such cartons have a latch flap. Eighteen cell cartons with a latch flap cannot be processed on existing standard packaging equipment. Standard packaging equipment has an egg carton holder that will not accept a carton any larger than 12" by 12" in the open position. To be processed on existing equipment, cartons must have overall dimensions no greater than 12".times.12" when in the open position.
It is an object of the present invention to provide an egg carton with an eighteen cell configuration which can be thermoformed from a plastic sheet and which can be processed on existing packaging equipment.